Abstract

In February 2000 the Shuttle Radar Topography Mission mapped 80% of the earth surface using the first space borne single pass SAR interferometer. On board were two radar systems, a US system operating in C-band and a German/Italian system operating in X-band. At the German Aerospace Center DLR the global X-band data set is processed to a global digital elevation model (DEM). Even if the single pass mode provides better coherence than previous dual pass missions, the high complexity of the system poses a challenging problem when it comes to precise calibration. Since the overall terrain map shall be homogenous all over the world, all electric and geometric subsystems must be characterized precisely. The tasks include synchronizing clocks, and modelling the system's response to changing operation modes, changing temperatures and inevitable motion of the space shuttle platform. In many aspects the SRTM SAR system will be the best known and most precise calibrated SAR sensor flown so far. The paper describes the technical challenges and the techniques applied to isolate the critical parameters. It will show the procedures that were applied to compensate for the mechanical and electrical error sources. Final results will be shown demonstrating the quality and the specific properties of SRTM X-SAR data.